A Department of Sustainability and Environment spokeswoman said the department was considering running tests on the bloom, which is being monitored. The department could not rule out closing the beach.

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The pinkish, tan-coloured material looks like oil and is not believed to be related to a red algal bloom off Bondi in Sydney earlier this week. The spokeswoman said algal blooms occurred when there had been heavy rains followed by sunny and calm weather.

Beach users should avoid going near any algal bloom as it can cause skin irritation. Anyone who comes in contact with it should wash it off with clean water.

"Algal blooms are rarely harmful to human health, however DSE and the Surf Coast Shire advise people to avoid contact with any water that looks murky or discoloured," a department statement said.

Alecia Bellgrove, senior lecturer in marine biology and ecology at Deakin University, said the water looked like a case of ‘‘red tide’’ and she warned swimmers to keep away from the bloom and to avoid swallowing the water.

‘‘The public health warning is if you have gone swimming in the area and you feel unwell you should see your doctor,’’ Dr Bellgrove said.

‘‘These micro toxins can act in complex ways and if it is a toxic species it can have a variety of effects,’’ she said.

Dr Bellgrove said there were many different types of red algal bloom and the only way to be certain about its toxicity was to test it.

She said shellfish were most likely to be affected but the area is not known for commonly eaten species such as mussels and oysters.

‘‘I wouldn’t be eating any pippis from the beach,’’ Dr Bellgrove said, adding that it could cause fish or birds to die.

She said the bloom’s position meant it was likely to disperse quickly.

Freelance photographer Drew Ryan said he saw the bloom come ashore on Wednesday and had seen people playing in the water.

Algal blooms are made up of tiny, floating marine plants. Toxic blue-green algae, like those that occur in Victoria's lakes, dams and rivers do not grow in the salty marine waters.

Lifesaving Victoria spokeswoman Jennifer Roberts said guards at Lorne and Torquay had seen the bloom and were making public announcements to swimmers to stay away from the discoloured water.

At Torquay, lifesavers had seen the bloom come in to shore and it had forced them to shift the safety flags and the patrol area further down the beach.

Ms Roberts said the bloom was behind the surf break at Lorne and guards were using inflatable rescue boats to warn surfers who ventured into the area.

More information about the blooms is available through Visitor Information Centres.

Suspected algal blooms, discoloured water or floating slicks should be reported to the Environment Protection Authority on 1300 372 842.